Cancer treatment can be approached by several modes of therapy, including surgery, radiation, chemotherapy, or a combination of any of these treatments. Among them, chemotherapy is indispensable for inoperable or metastatic forms of cancer.
The microtubule system of eukaryotic cells is an important target for developing anti-cancer agents. More specifically, tubulin polymerization/depolymerization is a popular target for new chemotherapeutic agents. A variety of clinically used compounds (e.g., paclitaxel, epothilone A, vinblastine, combretastatin A-4, dolastatin 10, and colchicine) target tubulin polymerization/depolymerization and disrupt cellular microtubule structures, resulting in mitotic arrest and inhibition of the growth of new vascular epithelial cells. See, e.g., Jordan et al. (1998) Med. Res. Rev. 18: 259-296. Thus, those compounds may have the ability to inhibit excessive angiogenesis, which occurs in diseases such as cancer (both solid and hematologic tumors), cardiovascular diseases (e.g., atherosclerosis), chronic inflammation (e.g., rheutatoid arthritis or Crohn's disease), diabetes (e.g., diabetic retinopathy), macular degeneration, psoriasis, endometriosis, and ocular disorders (e.g., corneal or retinal neovascularization). See, e.g., Griggs et al. (2002) Am. J. Pathol. 160(3): 1097-103.
Take combretastatin A-4 (CA-4) for example. CA-4, isolated by Pettit and co-workers in 1982 (Can. J. Chem. 60: 1374-1376), is one of the most potent anti-mitotic agents derived from the stem wood of the South African tree Combretum caffrum. This agent shows strong cytotoxicity against a wide variety of human cancer cells, including multi-drug resistant cancer cells. See, e.g., Pettit et al. (1995) J. Med. Chem. 38: 1666-1672; Lin et al. (1989) Biochemistry 28: 6984-6991; and Lin et al. (1988) Mol. Pharmacol. 34: 200-208. CA-4, structurally similar to colchicines, possesses a higher affinity for the colchicine binding site on tubulin than colchicine itself. Pettit et al. (1989) Experientia 45: 209-211. It also has been shown to possess anti-angiogenesis activity. See Pinney et al. WO 01/68654A2. The low water-solubility of CA-4 limits its efficacy in vivo. See, e.g., Chaplin et al. (1999) Anticancer Research 19: 189-195; and Grosios et al. (1999) Br. J. Cancer 81: 1318-1327.
Identification of compounds that also target the microtubule system (e.g., tubulin polymerization/depolymerization) can lead to new therapeutics useful in treating or preventing cancer or symptoms associated with cancer.